Various systems require electrical coupling between electrical devices disposed within a sealed enclosure or housing and devices or systems external to the enclosure. Oftentimes, such electrical coupling needs to withstand various environmental factors such that a conductive pathway or pathways from the external surface of the enclosure to within the enclosure remains stable. For example, implantable medical devices (IMDs), e.g., cardiac pacemakers, defibrillators, neurostimulators, and drug pumps, which include electronic circuitry and one or more power sources, require an enclosure or housing to contain and seal these elements within a body of a patient. Many of these IMDs include one or more electrical feedthrough assemblies to provide electrical connections between the elements contained within the housing and components of the IMD external to the housing, for example, one or more sensors, electrodes, and lead wires mounted on an exterior surface of the housing, or electrical contacts housed within a connector header, which is mounted on the housing to provide coupling for one or more implantable leads, which typically carry one or more electrodes and/or one or more other types of physiological sensors. A physiological sensor, for example a pressure sensor, incorporated within a body of a lead may also require a hermetically-sealed housing to contain electronic circuitry of the sensor and an electrical feedthrough assembly to provide electrical connection between one or more lead wires, which extend within the implantable lead body, and the contained circuitry.
IMDs for monitoring a physiological condition and/or delivering a therapy can include one or more physiological sensors. Such sensors can provide one or more signals related to one or more physiological conditions of a patient state. Examples of such IMDs include heart monitors, pacemakers, implantable cardioverter defibrillators (ICDs), myostimulators, neurological stimulators, drug delivery devices, insulin pumps, glucose monitors, etc.
Optical sensors may be employed in IMDs as physiological sensors configured to detect changes in light modulation by, for example, a body fluid or tissue measurement volume due to a change in a physiological condition in the body fluid or tissue. Such optical sensors can be used, for example, to detect changes in metabolite levels in the blood, such as oxygen saturation levels or glucose level, or changes in tissue perfusion. A typical optical sensor can include one or more light sources and one or more detectors that are adapted to detect light emitted by the light sources and modulated by, e.g., body fluid or tissue measurement volume.
Monitoring such physiological conditions provides useful diagnostic measures and may be used in managing therapies for treating a medical condition. For example, a decrease in blood oxygen saturation or in tissue perfusion may be associated with insufficient cardiac output or respiratory function. Thus, monitoring such conditions may allow an implantable medical device to respond to a decrease in oxygen saturation or tissue perfusion, for example, by delivering electrical stimulation therapies to the heart to restore a normal hemodynamic function.